[llvm] [AMDGPU] ISel for @llvm.amdgcn.cs.chain intrinsic (PR #68186)

[Jay Foad via llvm-commits]

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@@ -665,6 +665,50 @@ def : GCNPat<
   (SI_TCRETURN_GFX Gfx_CCR_SGPR_64:$src0, (i64 0), i32imm:$fpdiff)
 >;
 
+// Pseudo for the llvm.amdgcn.cs.chain intrinsic.
+// This is essentially a tail call, but it also takes a mask to put in EXEC
+// right before jumping to the callee.
+class SI_CS_CHAIN_TC<
+    ValueType execvt,
+    RegisterOperand execrc = !if(!eq(execvt, i32), SSrc_b32, SSrc_b64)>
+    : SPseudoInstSI <(outs),
+      (ins CCR_SGPR_64:$src0, unknown:$callee, i32imm:$fpdiff, execrc:$exec)> {
+  let FixedSize = 0;
+  let isCall = 1;
+  let isTerminator = 1;
+  let isBarrier = 1;
+  let isReturn = 1;
+  let UseNamedOperandTable = 1;
+  let SchedRW = [WriteBranch];
+  let isConvergent = 1;
+
+  let WaveSizePredicate = !if(!eq(execvt, i32), isWave32, isWave64);
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jayfoad wrote:

It's a matter of taste I guess, but you could just pass the predicate in as a second template argument.

https://github.com/llvm/llvm-project/pull/68186